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Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.

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At least 451 records · Page 25
All sourcesNASA NTRSDOE OSTI
DOE OSTI2015

Implementation and Validation of Reference Sensitivity Profile Calculations in TRIPOLI 4 - 14247

In current neutron transport calculations, particularly on continuous-energy Monte-Carlo codes, the major source of uncertainty is coming from nuclear data. In order to improve nuclear data evaluations, integral experiments are used. Feedback is then precisely obtained by re-estimating cross-section levels and correlations according to their sensitivity. k{sub eff}-sensitivity coefficients are traditionally obtained using deterministic codes since hands-on methods were not yet implemented in continuous energy Monte Carlo codes. In this paper, an Iterated-Fission-Probability-based method newly developed in the continuous energy Monte Carlo code TRIPOLI-4 will be used to calculate sensitivity coefficient breakdown on isotopes and reactions and results will be compared to those of ERANOS deterministic code. Objective is twofold: to show the reliability of the new TRIPOLI-4 method and to identify where and why profiles are slightly different. Sensitivity profiles, forward and adjoint fluxes are thus meticulously compared using a fine 1968-group energy structure. An OECD international benchmark (Uncertainty Analysis for Criticality Safety Assessment - UACSA - Phase III) is taken as working example to enforce validation and to compare to independent results (e.g. MCNP-6). This benchmark is constituted of two bare spheres filled with homogeneous mixture of uranium and polyethylene (respectively 2% and 50% U-235 enrichments) and gives an overview of issues encountered in thermal reactor cores. Several energy-group structures (1968G, 172G, 33G) are also tested in ERANOS to identify multi-group and implicit effects. Lessons learnt are that continuous Monte Carlo methods seem to be mature and compare well with deterministic codes. Only damper the U-238 elastic - and on certain conditions the U-238 capture - sensitivity coefficient for which difference can reach 30% between TRIPOLI-4 and ERANOS. Indeed concerning U-238, implicit effects are emphasized and multi-group theory remains limited by hypothesis; even a 1968-group structure is not refined enough to properly calculate U-238 elastic scattering k{sub eff}-sensitivity. This reference 3D continuous-energy sensitivity capability in TRIPOLI4-IFP will be extensively used in the uncertainty automated tool RIB of the French Criticality-Safety package CRISTAL. (authors)

42 ENGINEERING↗
DOE OSTI2022

Quantification of the importance of the modeling fidelity in the Best Estimate Plus Uncertainty analysis

In this work, the multi-physics coupling of CTF-PARCS for both steady-state and transient simulations is evaluated focusing on the quantification of the importance of the modeling fidelity when applied to the Best Estimate Plus Uncertainty safety analysis. For the steady-state, a Picard iteration approach is adopted in the coupled code while for the transient an explicit approach has been developed as a first step. The CTF-PARCS coupling is applied to the REA at HFP BOC scenario proposed in the exercise I-2c of LWR-UAM benchmark Phase III. Two different modeling choices are investigated for the nominal calculations. The first consists of including the 3D burnup information in CTF, and the second of modeling the spacers grids in both PARCS and CTF. It is observed that due to the degradation of the fuel thermal conductivity, the 3D burnup inclusion in CTF leads to significant higher centerline temperatures than the base case, with a difference up to 300 K. The spacer grids modeling shows the expected power and temperature decrease in the axial positions of the spacer grids. For the uncertainty quantification study, the multi-physics modeling including the burnup information in CTF is used. The results show that the inserted reactivity has a relative standard deviation of 13.6% mainly attributed to the nuclear data. The maximum linear power has a relative standard deviation of 16.2% due to the nuclear data as well, while the maximum centerline temperature has a relative standard deviation of 3.5% primarily caused by the fuel thermal conductivity. (authors)

21 SPECIFIC NUCLEAR REACTORS AND ASSOCIATED PLANTS↗
DOE OSTI2024

Smart Pixels: In-pixel AI for on-sensor data filtering

We present a smart pixel prototype readout integrated circuit (ROIC) designed in CMOS 28 nm bulk process, with in-pixel implementation of an artificial intelligence (AI) / machine learning (ML) based data filtering algorithm designed as proof-of-principle for a Phase III upgrade at the Large Hadron Collider (LHC) pixel detector. The first version of the ROIC consists of two matrices of 256 smart pixels, each 25$\times$25 $\mu$m$^2$ in size. Each pixel consists of a charge-sensitive preamplifier with leakage current compensation and three auto-zero comparators for a 2-bit flash-type ADC. The frontend is capable of synchronously digitizing the sensor charge within 25 ns. Measurement results show an equivalent noise charge (ENC) of $\sim$30e$^-$ and a total dispersion of $\sim$100e$^-$ The second version of the ROIC uses a fully connected two-layer neural network (NN) to process information from a cluster of 256 pixels to determine if the pattern corresponds to highly desirable high-momentum particle tracks for selection and readout. The digital NN is embedded in-between analog signal processing regions of the 256 pixels without increasing the pixel size and is implemented as fully combinatorial digital logic to minimize power consumption and eliminate clock distribution, and is active only in the presence of an input signal. The total power consumption of the neural network is $\sim$ 300 $\mu$W. The NN performs momentum classification based on the generated cluster patterns and even with a modest momentum threshold, it is capable of 54.4% - 75.4% total data rejection, opening the possibility of using the pixel information at 40MHz for the trigger. The total power consumption of analog and digital functions per pixel is $\sim$ 6 $\mu$W per pixel, which corresponds to $\sim$ 1 W/cm$^2$ staying within the experimental constraints.

46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND ↗
DOE OSTI2018

Pipe Overpack Container Fire Testing: Phase I II & III.

The Pipe Overpack Container (POC) was developed at Rocky Flats to transport plutonium residues with higher levels of plutonium than standard transuranic (TRU) waste to the Waste Isolation Pilot Plant (WIPP) for disposal. In 1996 Sandia National Laboratories (SNL) conducted a series of tests to determine the degree of protection POCs provided during storage accident events. One of these tests exposed four of the POCs to a 30-minute engulfing pool fire, resulting in one of the 7A drum overpacks generating sufficient internal pressure to pop off its lid and expose the top of the pipe container (PC) to the fire environment. The initial contents of the POCs were inert materials, which would not generate large internal pressure within the PC if heated. POCs are now being used to store combustible TRU waste at Department of Energy (DOE) sites. At the request of DOE’s Office of Environmental Management (EM) and National Nuclear Security Administration (NNSA), starting in 2015 SNL conducted a series of fire tests to examine whether PCs with combustibles would reach a temperature that would result in (1) decomposition of inner contents and (2) subsequent generation of sufficient gas to cause the PC to over-pressurize and release its inner content. Tests conducted during 2015 and 2016 were done in three phases. The goal of the first phase was to see if the PC would reach high enough temperatures to decompose typical combustible materials inside the PC. The goal of the second test phase was to determine under what heating loads (i.e., incident heat fluxes) the 7A drum lid pops off from the POC drum. The goal of the third phase was to see if surrogate aerosol gets released from the PC when the drum lid is off. This report will describe the various tests conducted in phase I, II, and III, present preliminary results from these tests, and discuss implications for the POCs.

12 MANAGEMENT OF RADIOACTIVE AND NON-RADIOACTIVE W↗
DOE OSTI2020

High-pressure polymorphism in pyridine

Single crystals of the high-pressure phases II and III of pyridine have been obtained by in situ crystallization at 1.09 and 1.69 GPa, revealing the crystal structure of phase III for the first time using X-ray diffraction. Phase II crystallizes in P 2 1 2 1 2 1 with Z ′ = 1 and phase III in P 4 1 2 1 2 with Z ′ = ½. Neutron powder diffraction experiments using pyridine-d 5 establish approximate equations of state of both phases. The space group and unit-cell dimensions of phase III are similar to the structures of other simple compounds with C 2v molecular symmetry, and the phase becomes stable at high pressure because it is topologically close-packed, resulting in a lower molar volume than the topologically body-centred cubic phase II. Phases II and III have been observed previously by Raman spectroscopy, but have been mis-identified or inconsistently named. Raman spectra collected on the same samples as used in the X-ray experiments establish the vibrational characteristics of both phases unambiguously. The pyridine molecules interact in both phases through CH...π and CH...N interactions. The nature of individual contacts is preserved through the phase transition between phases III and II, which occurs on decompression. A combination of rigid-body symmetry mode analysis and density functional theory calculations enables the soft vibrational lattice mode which governs the transformation to be identified.

36 MATERIALS SCIENCE↗
DOE OSTI2016

CHAOS. III. GAS-PHASE ABUNDANCES IN NGC 5457

We present Large Binocular Telescope observations of 109 H ii regions in NGC 5457 (M101) obtained with the Multi-Object Double Spectrograph. We have robust measurements of one or more temperature-sensitive auroral emission lines for 74 H ii regions, permitting the measurement of “direct” gas-phase abundances. Comparing the temperatures derived from the different ionic species, we find: (1) strong correlations of T [N ii] with T [S iii] and T [O iii], consistent with little or no intrinsic scatter; (2) a correlation of T [S iii] with T [O iii], but with significant intrinsic dispersion; (3) overall agreement between T [N ii], T [S ii], and T [O ii], as expected, but with significant outliers; (4) the correlations of T [N ii] with T [S iii] and T [O iii] match the predictions of photoionization modeling while the correlation of T [S iii] with T [O iii] is offset from the prediction of photoionization modeling. Based on these observations, which include significantly more observations of lower excitation H ii regions, missing in many analyses, we inspect the commonly used ionization correction factors (ICFs) for unobserved ionic species and propose new empirical ICFs for S and Ar. We have discovered an unexpected population of H ii regions with a significant offset to low values in Ne/O, which defies explanation. We derive radial gradients in O/H and N/O which agree with previous studies. Our large observational database allows us to examine the dispersion in abundances, and we find intrinsic dispersions of 0.074 ± 0.009 in O/H and 0.095 ± 0.009 in N/O (at a given radius). We stress that this measurement of the intrinsic dispersion comes exclusively from direct abundance measurements of H ii regions in NGC 5457.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2015

Mono- and polynucleation, atomistic growth, and crystal phase of III-V nanowires under varying group V flow

We present a refined model for the vapor-liquid-solid growth and crystal structure of Au-catalyzed III-V nanowires, which revisits several assumptions used so far and is capable of describing the transition from mononuclear to polynuclear regime and ultimately to regular atomistic growth. We construct the crystal phase diagrams and calculate the wurtzite percentages, elongation rates, critical sizes, and polynucleation thresholds of Au-catalyzed GaAs nanowires depending on the As flow. We find a non-monotonic dependence of the crystal phase on the group V flow, with the zincblende structure being preferred at low and high group V flows and the wurtzite structure forming at intermediate group V flows. This correlates with most of the available experimental data. Finally, we discuss the atomistic growth picture which yields zincblende crystal structure and should be very advantageous for fabrication of ternary III-V nanowires with well-controlled composition and heterointerfaces.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2026

Efficient bidirectional quantum frequency conversion between telecom and visible bands using adaptively phase-matched III-V nanophotonic waveguides

Quantum frequency conversion (QFC) is essential for interfacing quantum systems operating at different wavelengths and for realizing scalable quantum networks. Despite extensive progress, achieving QFC with simultaneous high efficiency, low pump power, minimal noise, broad bandwidth, and pump-wavelength flexibility remains challenging. Here, we demonstrate efficient, low-noise, and bidirectional QFC between the telecom (1550-nm) and visible (780-nm) bands using unpoled indium gallium phosphide (InGaP) χ (2) nanophotonic waveguides, eliminating the need for a long-wavelength pump. Leveraging the large nonlinear susceptibility of InGaP together with adaptive phase-matching control, we obtain 27% (55%) internal efficiency in a 6-mm (2.5-mm)-long waveguide with a low pump power of 20 mW (50 mW) and a noise flux spectral density of 10 −4 counts per second per hertz at signal–pump detuning of 20 nm. These results mark a significant advance in integrated nonlinear photonics for high-performance QFC, facilitating the development of versatile and scalable quantum networks.

Hu, Jierui [Univ. of Illinois at Urbana-Champaign,↗
DOE OSTI2019

Antimonite Complexation with Thiol and Carboxyl/Phenol Groups of Peat Organic Matter

Peatlands and other wetlands with abundant natural organic matter (NOM) are important sinks for antimony (Sb). While formation of Sb(III) sulfide phases or Sb(III) binding to NOM are discussed to decrease Sb mobility, the exact binding mechanisms remain elusive. Here, we reacted increasing sulfide concentrations with purified model peat at pH 6, forming reduced organic sulfur species, and subsequently equilibrated the reaction products with 50 μM of antimonite under anoxic conditions. Sulfur solid-phase speciation and the local binding environment of Sb were analyzed using X-ray absorption spectroscopy. We found that 85% of antimonite was sorbed by untreated peat. Sulfide-reacted peat increased sorption to 98%. Shell-by-shell fitting of Sb K -edge X-ray absorption fine structure spectra revealed Sb in untreated peat bound to carboxyl or phenol groups with average Sb–carbon distances of ~2.90 Å. With increasing content of reduced organic sulfur, Sb was progressively coordinated to S atoms at distances of ~2.45 Å and Sb–carbon distances of ~3.33 Å, suggesting increasing Sb–thiol binding. Iterative target factor analysis allowed exclusion of reduced inorganic Sb–sulfur phases with similar Sb–sulfur distances. In conclusion, even when free sulfide concentrations are too low for formation of Sb–sulfur precipitates, peat NOM can sequester Sb in anoxic, sulfur-enriched environments.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2018

Cold Commissioning Simulant Selection for the Hanford Tank Waste Treatment Plant LAW Facility - 18465

Commissioning the Low-Activity Waste (LAW) Facility of the Hanford Tank Waste Treatment and Immobilization Plant (WTP) will require large volumes (∼2,000,000 liters) of a non-radioactive, chemically analogous waste simulant. Cold commissioning will provide for operator training in an integrated facility, demonstration of mechanical process equipment capacity, environmental performance demonstration of emissions control systems, and process control systems shakedown and tuning. Selection of the cold commissioning simulant is following a structured four-phase process to arrive at the preferred composition and recipe. Phases I, II and III are complete. Phase I laid the framework for decision making with preparation of a Project Management Plan, an update to the Simulant Development, Approval, Validation, and Documentation procedure, and a kickoff meeting to gather stakeholder input into the simulant definition and selection criteria. Phase II consisted of a comprehensive literature search and compilation of LAW simulant recipes, followed by initial screening against the selection criteria identified in Phase I. This process identified 72 candidate simulant recipes and down-selected 9 for further study. Phase III studies involved a) statistical comparisons of the similarity of candidate simulant compositions to the tank waste feed vector, b) process modelling of the commissioning sequence with each simulant to estimate glass former and simulant material consumption, offgas and effluent volumes and compositions, and product glass volumes and compositions, and c) evaluation of simulants against the immobilized LAW glass composition algorithm to determine allo able waste loading to ensure compliance with product specifications and process constraints. The results of these studies identified two of the candidate recipes to be carried forward to full-scale testing. Phase IV consists of testing these two recipes at vendor facilities to determine scalability, fabricability, and stability of the simulants when produced at industrial scale. Scalability is the ability to take a recipe from bench scale (1 to 40 liters) batch size to full scale (>35,000 liters) batch size. Fabricability is the ability of a recipe to be prepared in large batches without the need for complex or expensive mechanical equipment, heating, or cooling systems. Stability is the ability of a simulant to withstand long term storage and variations in environmental conditions without unacceptable changes in key characteristics (the set of chemical, physical, and rheological parameters that the simulant is intended to exhibit during cold commissioning tests). Simulants will also be tested for compatibility with other startup material (i.e., frit), tuning simulants, and environmental performance demonstration test spiking solutions to ensure against unexpected situations. Using a structured process is essential when making high impact decisions such as waste simulant selection. Proper planning and a clear explanation of how the decision process will unfold is key to obtaining stakeholder buy-in as more information is gathered. The documentation resulting from this structured selection process will be compiled and summarized in a Cold Commissioning Simulant Definition deliverable due to the Department of Energy 24 months before the start of Cold Commissioning. (authors)

12 MANAGEMENT OF RADIOACTIVE AND NON-RADIOACTIVE W↗
DOE OSTI2015

EERC Center for Biomass Utilization 2008-2010. Phases I-III

The U.S. Department of Energy (DOE) Energy Information Administration (EIA) projects nonhydro renewable electric energy increases of 140% and liquid transportation biofuels growing by 32,200 barrels a day between 2012 and 2040 (U.S. Energy Information Administration, 2014). This is the EIA base case scenario, and this outlook could be a low estimate depending on the many assumptions involved in making such projections, not the least of which are climate change and the resultant legislation. The climate change postulate is based on increasing levels of CO 2 being introduced into the atmosphere through anthropogenic activity such as fossil fuel combustion for energy use. Renewable energy, and biomass conversion to energy in particular, is a net-zero CO 2 emission generator. When biomass is converted to energy, it emits CO 2 ; however, this CO 2 is balanced in a cycle where the production of biomass removes CO 2 from the atmosphere for growth and then releases it back into the atmosphere to be taken up by new growth of biomass feedstocks for energy. In comparison, fossil fuels are examples of CO 2 that has been removed from the atmosphere and sequestered and which, when converted to energy, is a new addition to the atmospheric levels of CO 2 , which has been linked to climate change. While recent advances in technology used for extracting oil and gas from tight formations have increased the availability of fossil fuels for energy, the end game needs to focus on providing sustainable energy sources for the United States as well as the world. If, in the future, legislation is enacted that places a fee on atmospheric CO 2 emissions, this may make the use of biomass for energy more economically attractive, increasing its use. Research that focuses on the future sustainability of energy production is part of the answer to bringing about game-changing technologies that can provide energy in a timely, reliable, sustainable fashion.

09 BIOMASS FUELS↗
NASA NTRS1961

Photosynthetic Gas Exchange in the Closed Ecosystem for Space. Phase II, Part III. Screening for Thermophilic Algae and Mutation Studies

An algal screening and mutation study was undertaken to obtain algae superior to Chlorella 71105 for use in a photosynthetic gas exchanger. Of the forty-four thermophilic algae studied, eighteen appeared to have growth rates as great as Chlorella 71105. Optimization of the physical and chemical environments of these strains is recommended as a way to further improve growth rates and concomitant oxygen production. The mutation study revealed that Chlorella 71105 is relatively resistant to germicidal ultraviolet radiation. No high temperature mutants of Chlorella 71105 were found.

ALGAE↗